Methods for improving display luminance in color display devices have been proposed. As an example, there is a liquid crystal display device in which one unit pixel is constituted by arranging a red (R) color pixel, a green color (G) pixel, a blue color (B) pixel and a white color (W) pixel in a row direction in a predetermined order.
In recent years, liquid crystal display devices with a vertical alignment (VA) mode and an in-plane switching (IPS) mode are developed. In the VA mode, liquid crystal molecules are aligned vertically in the initial state and then inclined while a voltage is being applied thereto in order to vary birefringence. The VA mode realizes transmittance (white) and non-transmittance (black) using this birefringence varied by the inclination. In the IPS mode, liquid crystal molecules are aligned in-plane to be parallel with a substrate major surface in the initial state and then rotated in-plane while a voltage is being applied thereto in order to vary birefringence. The IPS mode realizes transmittance (white) and non-transmittance (black) using this birefringence varied by the rotation.
In the VA mode, the liquid crystal molecules between pixels of different colors do not change their original inclination significantly as compared to the IPS mode. Thus, the VA mode can narrow down the light shielding widths between the color pixels for higher aperture ratio and luminescence. On the other hand, optical rotatory dispersion or wavelength dispersion in the liquid crystal layer affects pixel hues in accordance with the inclination of the liquid crystal molecules. When a unit pixel is composed of general three color pixels of red, green and blue, a voltage value of each of red color pixel, green color pixel, and blue color pixel is adjusted to correspond to gradation values for achieving a chromaticity maintaining a white balance. However, when a unit pixel is composed of four color pixels of red, green, blue and white, a blue shift phenomenon in which the hue of the white color pixel changes bluish appears conspicuously, and a sufficient chromaticity adjustment in three color pixels of red, green and blue becomes difficult.